Modifying gravity is called "cheating"

Gizmodo reports:

A fight over the very nature of the universe has turned ugly on social media and in the popular science press, complete with accusations of “cheating” and ad hominem attacks on Twitter. Most of the universe is hiding, and some scientists disagree over where it has gone.

It’s quite literally a story as old as time. Wherever you look in the cosmos, things don’t seem to add up. Our human observations of the universe’s structure—as far back as we can observe—suggest that there’s around five times more mass than we see in the galaxies, stars, dust, planets, brown dwarfs, and black holes that telescopes have observed directly. We call this mystery mass, or the mystery as a whole, “dark matter.”

Several thousand physicists researching these dark matter-related mysteries will tell you that dark matter is a particle, the way that electrons and protons are particles, that only appears to interact with other known particles via the gravitational pull of its mass. But there are a few dozen physicists who instead think that a set of ideas called “modified gravity” might one day explain these mysteries. Modified gravity would do away with the need for dark matter via a tweak to the laws of gravity. ...

Then, in June, the most sensitive dark matter particle-hunting experiment, called XENON, announced it had once again failed to find a dark matter particle. A story titled “Is Dark Matter Real?” followed in the August issue of Scientific American, ...

“It’s only if you ignore all of modern cosmology that the modified gravity alternative looks viable. Selectively ignoring the robust evidence that contradicts you may win you a debate in the eyes of the general public. But in the scientific realm, the evidence has already decided the matter, and 5/6ths of it is dark.”

In other words, it is a cheat to tweak the laws of gravity to accommodate the slow galaxy rotation, but not cheat to hypothesize a new particle.

Hoping for a dark matter particle was one of the main reasons for believing in SUSY, as SUSY requires about 100 new particles. Maybe the lightest one is the dark matter particle.

Another little controversy is whether the evidence for dark matter already contradicts the Standard Model. Not necessarily. Wilczek pushes axions as an explanation that I think is consistent with the SM.

Also, the SM only tries to explain strong, weak, and electromagnetic interactions. Dark matter could be some substance that does not interact with those forces, and thus could exist independently from the SM.

In Gizmodo’s conversations with 13 physicists studying dark matter, a pretty clear picture emerged: Dark matter as an undiscovered population of particles that influence the universe through gravity is the prevailing paradigm for a reason, and will continue as such until a theory comes along with the same predictive power for the universe’s grandest features.

It is odd to call the substance a particle. We only call electrons particles because of how they interact with light, but dark matter does not interact with light.

“Everywhere the dark matter theories make predictions, they get the right answers,” Scott Dodelson, a Carnegie Mellon physics professor, told Gizmodo. But he offered a caveat: “They can’t make predictions as well on small scales,” such as the scales of galaxies.

I am surprised that anyone would brag about a theory that only works on scales much larger than galaxies.

Billion new dollars for quantum computation

Peter Woit announces:

Moving through the US Congress is a National Quantum Initiative Act, which would provide over a billion dollars in funding for things related to quantum computation.

A billion dollars?!

IBM and Google both promised quantum supremacy in 2017. We have no announcement of QS, or any explanation for the failure.

I am not the only one saying it is impossible. See this recent Quanta mag article for other prominent naysayers.

If Congress were to have hearings on this funding, I would expect physicists to be extremely reluctant to throw cold water on lucrative funding for their colleagues. Maybe that is what is keeping Scott Aaronson quiet.

Previously Woit commented:

It’s remarkable to see publicly acknowledged by string theorists just how damaging to their subject multiverse mania has been, and rather bizarre to see that they attribute the problem to my book and Lee Smolin’s. The source of the damage is actually different books, the ones promoting the multiverse, for example this one.

This was induced by some string theorists still complaining about those books that appeared in around 2005.

It is bizarre for anyone to be bothered by some criticism from 13 years ago. The two books did not even say the same thing. You would think that the string theorists would just publish their rebuttal and move on.

Apparently they had no rebuttal, and they depended on everyone going along with the fiction that string theory was working.

Likewise, the quantum computation folks depend on everyone going along with the idea that we are about to have quantum computers (with quantum supremacy), and it will be a big technological advance. We don't need two books on the subject, as it is pretty obvious that IBM and Google are not delivering what they promised.

Professor arrested for pocketing $4 in tips

Quantum computer complexity theorist Scott Aaronson seems to have survived his latest personal struggle, with his worldview intact.

He bought a smoothie, paid with a credit card, and took the $4 in the tip jar. An employee approached him, and politely explained that the tip jar is for tips. He grudgingly gave $1 back.

The manager then called the cops, and cop interviewed him to confirm what he had done. He was still oblivious to what was going on, so the cop handcuffed him and arrested him. That got his attention, and the manager agreed to drop the charges when the $4 was returned.

There is a biography about physicist Paul Dirac that calls him "the world's strangest man" because of a few silly anecdotes about him being a stereotypical absent-minded professor. That biographer has not met Scott.

Scott says that it was all the fault of the smoothie maker for not clearly explaining to him that he does not get to take change from the tip jar if he pays with a credit card. Scott is correct that there was a failure of communication, and surely both sides are at least somewhat to blame.

I am not posting this to criticize Scott. Just read his blog where he posts enuf negative info about himself. If I wanted to badmouth him, I would just link to his various posts where he has admitted to be wrong about various things. I am inclined to side with him as a fellow nerd who is frustrated by those who fail to explain themselves in a more logical manner. I am just posting it because I think that it is funny. After all, Scott has been named as one of the 30 smartest people alive and also one of the top 10 smartest people. And yet there are people with about 50 less IQ points who have no trouble buying smoothies, or understanding a request to put the tip money back.

Copenhagen is rooted in logical positivism

From an AAAS Science mag book review:

Most physicists still frame quantum problems through the sole lens of the so-called “Copenhagen interpretation,” the loose set of assumptions Niels Bohr and his colleagues developed to make sense of the strange quantum phenomena they discovered in the 1920s and 1930s. However, he warns, the apparent success of the Copenhagen interpretation hides profound failures.

The approach of Bohr and his followers, Becker argues, was ultimately rooted in logical positivism, an early-20th-century philosophical movement that attempted to limit science to what is empirically verifiable. By the mid-20th century, philosophers such as Thomas Kuhn and W. V. O. Quine had completely discredited this untenable view of science, Becker continues. The end of logical positivism, he concludes, should have led to the demise of the Copenhagen interpretation. Yet, physicists maintain that it is the only viable approach to quantum mechanics.

As Becker demonstrates, the physics community’s faith in Bohr’s wisdom rapidly transformed into a pervasive censorship that stifled any opposition.

This is partially correct. Quantum mechanics, and the Copenhagen Interpretation were rooted in logical positivism. Much of XX century physics was influenced, for the better, by logical positivism and related views.

It is also true that XX century philosophers abandoned logical positivism, for largely stupid reasons. They decided that there was no such thing as truth.

This created a huge split between the scientific world, which searches for truth, and the philosophical world, which contends that there is no such thing as truth. These views are irreconcilable. Science and Philosophy have become like Astronomy and Astrology. Each thinks that the other is so silly that any conversation is pointless.

Unfortunately, many physicists are now infected with anti-positivist views of quantum mechanics, and say that there is something wrong with it. Those physicists complain, but have gotten nowhere with there silly ideas.

Einstein's 1905 relativity had no new dogmas

Lubos Motl writes:

Einstein's breakthrough was far deeper, more philosophical than assumed

Relativity is about general, qualitative principles, not about light or particular objects and gadgets

Some days ago, we had interesting discussions about the special theory of relativity, its main message, the way of thinking, the essence of Einstein's genius and his paradigm shift, and the good and bad ways how relativity is presented to the kids and others. ...

Did the physicists before Einstein spend their days by screaming that the simultaneity of events is absolute? They didn't. It was an assumption that they were making all the time. All of science totally depended on it. But it seemed to obvious that they didn't even articulate that they were making this assumption. When they were describing the switch to another inertial system, they needed to use the Galilean transformation and at that moment, it became clear that they were assuming something. But everyone instinctively thought that one shouldn't question such an assumption. No one has even had the idea to question it. And that's why they couldn't find relativity before Einstein.

Einstein has figured out that some of these assumptions were just wrong and he replaced them with "new scientific dogmas".

They did find relativity before Einstein. With all the formulas. In particular, what Einstein said about simultaneity and synchronization of clocks was straight from what Poincare said five years earlier.

Motl repeats the widespread belief that Einstein found relativity by repudiating conventional wisdom and introducing new dogmas. That is not true at all. The most widely accepted theoy on the matter was Lorentz's 1895 theory. Lorentz had already received a Nobel prize for it in 1902.

Einstein's big dogmas were that the speed of light is constant and motion is relative. Einstein later admitted that he got the constant speed of light straight from Lorentz. He also got the relativity postulate from Lorentz, although it was Poincare who really emphasized it, so maybe he got it from Poincare.

Einstein did later argue against rival theories, such as Abraham's, but he never claimed that Lorentz or Poincare were wrong about their relativity theories. Other authors referred to the "Lorentz-Einstein theory", as if there were no diffence.xxc Even when Einstein was credited with saying something different from Lorentz, he insisted that his theory was the same as Lorentz's.

Einstein did sometimes pretend to have made conceptual advances in his formulation of special relativity, such as with the aether and local time. But what Einstein said on these matters was essentially the same as what Lorentz said many years earlier.

The formulation of special relativity that is accepted today is the geometric spacetime version presented by Poincare and Minkowki, not Einstein's. Poincare and Minkowski did explain how their view was different from Lorentz's.

Was Copernicus really heliocentric?

Wikipedia current has a debate on whether the Copernican system was heliocentric. See the Talk pages for Nicolaus Copernicus and Copernican heliocentrism.

This is a diversion from the usual Copernicus argument, which is whether he was Polish or German. He is customarily called Polish, but nation-states were not well defined, and there is an argument that he was more German than Polish.

The main point of confusion is that Copernicus did not really put the Sun at the center of the Earth's orbit. It was displaced by 1/25 to 1/31 of the Earth's orbit radius.

It appears that the center of the Earth's orbit revolved around the Sun, but you could also think of the Sun as revolving around the center of the Earth's orbit.

So is it fair to say that the Sun is at the center of the universe? Maybe if you mean that the Sun is near the center of the planetary orbits. Or that the Sun was at the center of the fixed stars. Or that the word "center" is used loosely to contrast with an Earth-centered system.

In Kepler's system, and Newton's, the Sun is not at the center of any orbit, but at a focus of an ellipse. It was later learned that the Sun orbits around a black hole at the center of the Milky Way galaxy.

I am not sure why anyone attaches such great importance to these issue. Motion is relative, and depends on your frame of reference. The Ptolemy and Copernicus models had essentially the same scientific merit and accuracy. They mainly differed in their choice of a frame of reference, and in their dubious arguments for preferring those frames.

People act as if the Copernicus choice of frame was one of the great intellectual advances of all time.

Suppose ancient map makers put East at the top of the page. Then one day a map maker put North at the top of the page. Would we credit him for being a great intellectual hero? Of course not.

There is an argument that the forces are easier to understand if you choose the frame so that the center of mass is stationary. Okay, but that was not really Copernicus's argument. There were ancient Greeks who thought it made more sense to put the Sun at the center because it was so much larger than the Earth. Yes, they very cleverly figured out that the Sun was much larger. There is a good logic to that also, but it is still just a choice of frame.

How physicists discovered the math of gauge theories

We have seen that if you are looking for theories obeying a locality axiom, and if you adopt a geometrical view, you are inevitably led to metric theories like general relativity, and gauge theories like electromagnetism. Those are the simplest theories obeying the axioms.

Formally, metric theories and gauge theories are very similar. Both satisfy the locality and geometry axioms. Both define the fields as the curvature of a connection on a bundle. The metric theories use the tangent bundle, while the gauge theories use an external group. Both use tensor calculus to codify the symmetries.

The Standard Model of particle physics is a gauge theory, with the group being U(2)xSU(3) instead of U(1), and explains the strong, weak, and electromagnetic interactions.

Pure gauge theories predict massless particles like the photon. The Standard Model also has a scalar Higgs field that breaks some of the symmetries and allows particles to have mass.

The curious thing, to me, is why it took so long to figure out that gauge theories were the key to constructing local field theories.
Newton published his theory of gravity in 1682, but was unhappy about the action-at-a-distance. He would have preferred a local field theory, but he could not figure out how to do it. Maxwell figured it out for electromagnetism in 1865, based on experiments of Faraday and others.

Nobody figured out the symmetries to Maxwell’s equations until Lorentz and Poincare concocted theories to explain the Michelson-Morley experiment,in 1892-1905. Poincare showed in 1905 that a relativistic field theory for gravity resolves the action-at-a-distance paradoxes of Newtonian gravity. After Minkowski stressed the importance of the metric, the geometry, and tensor analysis to special relativity in 1908, Nordstrom, Grossmann, Einstein, and Hilbert figured out how to make gravity a local geometrical theory. Hermann Weyl combined gravity and electromagnetism into what he called a “gauge” theory in 1919.

Poincare turned electromagnetism into a geometric theory in 1905. He put a non-Euclidean geometry on spacetime, with its metric and symmetry group, and used the 4-vector potential to prove the covariance of Maxwell’s equations. But he did not notice that his potential was just the connection on a line bundle.

Electromagnetism was shown to be a renormalizable quantum field theory by Feynman, Schwinger and others in the 1940s. ‘tHooft showed that all gauge theories were renormalizable in 1970. Only after 1970 did physicists decide that gauge theories were the fundamental key to quantum field theory, and the Standard Model was constructed in the 1970s. They picked SU(3) for the strong interaction because particles had already been found that closely matched representations of SU(3).

It seems to me that all of relativity (special and general) and gauge theory (electromagnetism and the Standard Model) could have derived mathematically from general principles, with little or no reference to experiment. It could have happened centuries ago.

Perhaps the mathematical sophistication was not there. Characterizing geometries in terms of symmetry transformations and their invariants was described in Klein's Erlangen Program, 1872. Newton did not use a vector notation. Vector notation did not become popular until about 1890. Tensor analysis was developed after that. A modern understanding of manifolds and fiber bundles was not published until about 1950.

Hermann Weyl was a brilliant mathematician who surely had an intuitive understanding of all these things in about 1920. He could have worked out the details, if he had understood how essential they were to modern physics. Why didn’t he?

Even Einstein, who was supposedly the big advocate of deriving physics from first principles, never seems to have noticed that relativity could be derived from geometry and causality. Geometry probably would not have been one of his principles, as he never really accepted that relativity is a geometrical theory.

I am still trying to figure out who was the first to say, in print, that relativity and electromagnetism are the inevitable consequences of the geometrical and locality axioms. This seems to have been obvious in the 1970s. But who said it first?

Is there even a physics textbook today that explains this argument? You can find some of it mentioned in Wikipedia articles, such as Covariant formulation of classical electromagnetism, Maxwell's equations in curved spacetime - Geometric formulation, and Mathematical descriptions of the electromagnetic field - Classical electrodynamics as the curvature of a line bundle. These articles mention that electromagnetics fields can be formulated as the curvature of a line bundle, and that this is an elegant formulation. But they do not explain how general considerations of geometry and locality lead to the formulation.

David Morrison writes in a recent paper:

In the late 1960s and early 1970s, Yang got acquainted with James Simons, ... Simons identified the relevant mathematics as the mathematical theory of connections on fiber bundles ... Simons communicated these newly uncovered connections with physics to Isadore Singer at MIT ... It is likely that similar observations were made independently by others.

I attended Singer’s seminars in the 1970s, so I can confirm that it was a big revelation to him that physicists were constructing a standard model based on connections on fiber bundles, a subject where he was a leading authority. He certainly had the belief that mathematicians and physicists did not know they were studying the same thing under different names, and he knew a lot of those mathematicians and physicists.

String theorists like to believe that useful physical theories can be derived from first principles. Based on the above, I have to say that it is possible, and it could have happened with relativity. But it has never happened in the history of science.

If there were ever an example where a theory might have been developed from first principles, it would be relativity and electromagnetism. But even in that case, it appears that a modern geometric view of the theory was only obtained many decades later.